We use the term register to refer to particular varieties or styles of speaking and writing. Registers vary because the language is used for different purposes, in different contexts and for different audiences.
To cause (mail) to be recorded upon delivery to a post office for safeguarding against loss, theft, damage, etc.
In sociolinguistics, a register is a variety of language used for a particular purpose or in a particular communicative situation. For example, when speaking officially or in a public setting, an english speaker may be more likely to follow prescriptive norms for formal usage than in a casual setting for example by pronouncing words ending in -ing with a velar nasal instead of an alveolar nasal(e. Walking, not walkin), choosing words that are considered more formal (such as father vs.).